Obstructive sleep apnea syndrome (commonly referred to as obstructive sleep apnea, sleep apnea syndrome, and/or sleep apnea) is a medical condition that includes repeated, prolonged episodes of cessation of breathing during sleep. During a period of wakefulness, the muscles of the upper part of the throat passage of an individual keep the passage open, thereby permitting an adequate amount of oxygen to flow into the lungs. During sleep, the throat passage tends to narrow due to the relaxation of the muscles. In those individuals having a relatively normal-sized throat passage, the narrowed throat passage remains open enough to permit an adequate amount of oxygen to flow into the lungs. However, in those individuals having a relatively smaller-sized throat passage, the narrowed throat passage prohibits an adequate amount of oxygen from flowing into the lungs. Additionally, a nasal obstruction, such as a relatively large tongue, and/or certain shapes of the palate and/or the jaw of the individual, further prohibit an adequate amount of oxygen from flowing into the lungs.
An individual having the above-discussed conditions can stop breathing for one or more prolonged periods of time (e.g., ten seconds or more). The prolonged periods of time during which breathing is stopped, or apneas, are generally followed by sudden reflexive attempts to breathe. The reflexive attempts to breathe are generally accompanied by a change from a relatively deeper stage of sleep to a relatively lighter stage of sleep. As a result, the individual suffering from obstructive sleep apnea syndrome generally experiences fragmented sleep that is not restful. The fragmented sleep results in one or more of excessive and/or inappropriate daytime drowsiness, headache, weight gain or loss, limited attention span, memory loss, poor judgment, personality changes, lethargy, inability to maintain concentration, and depression.
Other medical conditions can also prevent individuals, including adults and infants, from receiving an adequate amount of oxygen into the lungs. For example, an infant who is born prematurely can have lungs that are not developed to an extent necessary to receive an adequate amount of oxygen. Further, prior to, during and/or subsequent to certain medical procedures and/or medical treatments, an individual can be unable to receive an adequate amount of oxygen.
Under these circumstances, it is known to use a ventilation interface to apply a positive pressure to the throat of the individual, thereby permitting an adequate amount of oxygen to flow into the lungs. In known ventilation interfaces, oxygen and/or room air containing oxygen is delivered through the mouth and/or nose of the individual.
Existing types of positive pressure applied by the known ventilation interface include continuous positive airway pressure (CPAP), in which a positive pressure is maintained in the throat passage throughout a respiratory cycle, bi-level positive airway pressure (BiPAP), in which a relatively high positive pressure is maintained during inspiration and a relatively low positive pressure is maintained during expiration, and intermittent mechanical positive pressure ventilation (IPPV), in which a positive pressure is applied when apnea is sensed (i.e., the positive airway pressure is applied intermittently or non-continuously), automatic positive airway pressure (APAP), in which a positive pressure is automatically tuned to provide the minimum required to maintain an unobstructed throat passage on a breath-by-breath basis.
Typical CPAP airflow generators can deliver air to patients at pressures between 4 and 20 cm H2O. More specialized units can delivery pressures up to 25 or even 30 cm H2O. Most patients typically require air delivered at pressures between 6 and 14 cm H2O.
One conventional ventilation interface for the application of positive pressure includes a face mask that covers both the nose and the mouth. U.S. Pat. No. 4,263,908 (Mizerak) discloses a nasal cannula having oral gas delivery means incorporated therein adapted to increase efficiency in providing gas, such as oxygen to a patient. U.S. Pat. No. 6,123,071 (Berthon-Jones et al) discloses a combination mouth and nasal mask for assisted respiration or CPAP. At least one other exemplary ventilation interface is disclosed by U.S. Patent Application Publications Nos. 2006/0124131 (Chandran et al.) and 2006/0174887 (Chandran et al.). Other face masks include configurations that cover only the nose or only the mouth. Standard masks have air supplied under pressure and use headgear or harnesses to hold the mask on a user.